Pulling valves

[sgmypod]

Have this 100pa monster head....is it possible to reduce power by pulling valves and if so do you also adjust ohmage of output(IE 4 valves 16ohm is 8ohm in 2)

[Woogie]

Would the ohmage even change? Cos the speakers are the same.

[FELINEGUITARS]

ohmage will change if you pull some valves even the though the speakers are the same

[sgmypod]

I thought that...but will it kill amp or change biasing

[Roobubba]

Of all people, I wasn't expecting Feline to use the "word" 'ohmage'...

[sgmypod]

*L*

[Will]

Of all people, I wasn't expecting Feline to use the "word" 'ohmage'...

I don't get it :?

Yeah, speakers take the load that the amp gives, half the power output, half the load the amp gives I think

[FELINEGUITARS]

Yeah - halve the output impedance setting

[Oli]

On one side of the transformer (the primary), you have the output section of the amplifier, and on the secondary coils, you have the speakers. Transformers work on a ratio system, so what happens on one side has to happen on the other- or else you end up with an imbalance, and mismatched impedance. By removing two of the valves from the power section, you halve the impedance, so you need to half the impedance on the speaker-side of things.

[Roobubba]

Yay, Baby Jesus no longer needs to cry :)

Roo

[sgmypod]

So 8ohm in 4valve(that I have set now on back) is now is 4ohm  when I remove 2 valves

[MrBump]

I'm out of my comfort zone with all this valve stuff, but are we SURE that dropping valves changes "ohmage" (to quote Johathan)?

Doesn't it depend more on the output transformer?

I know ask because when John Cooper did work on my Orange and re-valved/biased it, he dropped 2 output valves, but the ohm setting remained the same.  I don't think that he did any other work.

Again, I don't know, but thems the facts, innit?

Mark.

[the_bleeding]

dont pull valves. Sure it reduces wattage but it does NOT reduce volume by any noticeable amount. 3db is a very small difference for the risk you take doing it. Also, when you pull them, it makes your amp sound like shite. Your amp was designed for 4 valves, pulling 2 will make it sound gross. I have a halfpower switch on my amp, it effectively shuts off 2 valves. I relabeled it the "suck" switch because thats what it does.

[hamfist]

dont pull valves. Sure it reduces wattage but it does NOT reduce volume by any noticeable amount. 3db is a very small difference for the risk you take doing it. Also, when you pull them, it makes your amp sound like shitee. Your amp was designed for 4 valves, pulling 2 will make it sound gross. I have a halfpower switch on my amp, it effectively shuts off 2 valves. I relabeled it the "suck" switch because thats what it does.

 This is a very common story to hear from people who have tried halving the number of output valves, although I admit I have not tried it myself.

[MrBump]

dont pull valves. Sure it reduces wattage but it does NOT reduce volume by any noticeable amount. 3db is a very small difference for the risk you take doing it. Also, when you pull them, it makes your amp sound like shitee. Your amp was designed for 4 valves, pulling 2 will make it sound gross. I have a halfpower switch on my amp, it effectively shuts off 2 valves. I relabeled it the "suck" switch because thats what it does.

Hmmm...  I can't say I agree.  My Orange sounds amazing with just 2 EL34s.  Maybe it depends on the amp?

Mark.